Differential modes operation is usually used for common mode noise suppression. It can be used in many circuits such as a power amplifier (PA), a low noise amplifier (LNA), a mixer, and so on. However, the differential operation is not the mechanism for supporting multiple communication standards or multiple frequency bands.
The power amplifier is often required to provide a high swing and a low output impedance at its output, so matching networks or circuits are required to provide proper impedance transformation for multiple frequency bands in order to reach low output impedance at its output in different modes. In addition, mismatch and asymmetry (e.g., amplitude difference and/or phase difference) between the differential signals can degrade the output performance of the power amplifier.
Therefore, there is a need to design a matching network circuit and related matching network and power amplifier to achieve odd harmonic rejection in the differential mode, even harmonic rejection in the common mode, and symmetry improvement, so as to ensure the output performance of the power amplifier.